overcharged and struggling for a refund

I opened a contract with telkom mobile in March first debit order or R99.00 was supposed to be deducted end on april but instead the deducted R1300.00 end April 2015. I ccalled and they told me its for upgrading my packacge but this is the first telkom contract i ever had they promised to investigate ,I called them after a week they adviced they made a mistake with my billing ,a case number ***4 was provided to me and i was promised a refund but i called numerious times no one is willing to help me with the refund they always tell me about the SLA which extends everytime i call .A second case number ***0 was opened and my banking details were requested i confirmed everything with them but till today i havent received my money back, It has been a month sincve the deduction was made,I need the money as i want to pay other accounts that defaulted due to Telkom taking my money without outhorisation